1. Field of the Invention
The field of this invention relates to rotary torque actuators, and more specifically to an actuator wherein a rotary driving torque is produced by means of a linear force applied to the rotary member.
At the present time, rotary torque is developed by various devices such as, by way of example, vane-type actuators wherein rotary motion is imparted to a drive shaft as the result of a fluid media under pressure acting upon the surface of a vane configuration mounted to the drive shaft. Another type of mechanism utilizes a scotch yoke, wherein linear motion is transmitted to a bell crank member which, in turn, is attached to a rotably shaft.
Gear drive mechanisms are also used for converting linear force through a rack attached to a pinion on a drive shaft which converts the linear motion of the rack to rotary motion.
2. Description of the Prior Art
Applicant is aware of the following U.S. Patents, each of which relate to and disclose means for imparting rotary motion to a rotable drive shaft by the application of a linear motion to a mechanism which engages and is moved along and relative to, the shaft:
The K. H. Meyer U.S. Pat. No. 3,255,806 dated June 14, 1966 discloses a one-way fluid actuated hinge structure which comprises and elongate, one piece tubular housing 20 having end caps 30 and 31 through which the opposite ends of an elongate shaft 44 project. Piston 53 of a piston-assembly which includes a tubular skirt 60 and a tubular ball nut 58 is adapted to move within housing 20 axially along the spirally grooved portion 52 of the shaft 44 for imparting a turning torque thereto. In FIG. 4 a pair of pistons are disposed within the elongate housing for movement in opposite directions along shaft 80. The power and rotary functions are combined within one elongate housing, whereas applicant utilizes separate power and converter sections which are disposed in end-to-end tandem relationship. Meyer's elongate housing 20 comprises a pressurized vessel, whereas in applicants device the converter section comprises an unpressurized vessel containing lubricating fluid. No fluid pressure stresses are incurred, and, as such the design of the converter section is directed to its mechanical load carrying characteristics without regard for radial stresses induced by fluid operating pressures.
The W. F. Mitchell U.S. Pat. No. 3,153,986, dated Oct. 27, 1964 discloses a rotary torque actuator which comprises an elongate, one piece tubular housing 10 having end members 11 and 12. A piston 20 and a cam member 21 are housed within the cylinder. Shaft 34 and its associated rollers 51 are housed within the cylinder for rotation relative thereto. The cylinder is also provided with cam rollers 41 which engage the fluted cam tracks 71 of the cam member 21. As the piston and cam member 21 are advanced to the right incident to the introduction of passure media into the cylinder via port 29 the cam member is advanced, in telescoping relationship over an end of shaft 34. The introduction of fluid media into port 32 at the opposite end of housing 10 will shift the piston to its initial, fully retracted position. The reference, like Meyer, supra, combines the power and rotary functions of the actuator in one elongate housing which comprises a pressurized vessel. Furthermore, the rod assembly of Mitchell is complicated whereas applicants drive shaft is solid having elongate spiral grooves machined and ground into its outer surface.
The H. M. Geyer U.S. Pat. No. 2,804,053, dated Aug. 27, 1957, discloses a device which includes a locking mechanism for a linear or rotary actuator. An elongate, cylindrical body 10 is provided with ends-11 and 12. Piston rod 16 projects through end 11, and the other end of the piston rod is counterbored to accept fluted shaft 25 which enters the counterbore threadably through a hollow nut 23. The other end of the fluted shaft is secured to and carried by a friction brake (FIG. 6) which is incorporated in mounting cap 12. The linear movement of the piston, piston-rod assembly imparts rotary motion to shaft 25 via hollow nut 23. The fluid pressure which actuates the piston is used to unlock the friction brake, and when fluid pressure is withdrawn the friction brake is actuated for, thus, locking the piston rod relative to cylindrical body 10. This reference, like that of Meyer, and Mitchell combines the power and rotary functions of the actuator in one elongate housing which constitutes pressurized vessel.
The H. M. Geyer U.S. Pat. No. 3,133,476, dated May 19, 1964, discloses a rotary actuator which comprises a single, elongate, tubular member 10 which defines a cylinder having end members 12 and 14. Shaft 26 extends throughout the length of the cylinder, said shaft being journaled at its ends for rotary motion, and provided with internal ports 70 and 74. The central portion of the shaft is enlarged to provide a bulkhead 28. Tandem pistons 48-56 are provided at opposite ends of skirt 52 the outer surface of which is provided with flutes 80 which engage and traverse the elongate inside helix 84 of end member 14, thus imparting rotary motion to shaft 26. This reference, like those heretofore discussed combines the power and rotary functions of the actuator in a single elongate housing, and the comparatively large diameter and length of the fluted members, together with the chamber defined by piston head 48, skirt 52, and piston 56 impose serious mechanical limitations on the potential force loading. The wall thickness of skirt 52 must be sufficiently thick to withstand the operating pressures, and skirt 86 must have sufficient strength to carry the rotary load to rotary member 14, together with sufficient fluid geometry to properly drive and mesh with skirt 52.
The J. E. Davis U.S. Pat. No. 3,090,244, dated May 21, 1963 discloses a rotary actuator which comprises a single cylinder defined by a single, elongate, tubular member 10 having end caps 12 and 14. A through shaft 18 having spline teeth 64 and 76 on opposite sides of a central bulkhead 86, extends through the end caps. A piston assembly 30 which includes a nut 42, annuli 46 and 48, tubular member 44, and various seals traverses the interior of member 10. The design of this reference is exceedingly complex utilizing a multiplicity of splined members and seals which occurs by reason of the integration of both the power and rotary conversion functions within the same housing number 10. The device is further complicated by the projection of drive splines 20 on both ends of the actuator being driven by the same mechanism.
The J. C. Miller U.S. Pat. No. 2,974,646, dated Mar. 14, 1961, discloses a rotary actuator which comprises a single cylinder defined by an elongate tube 10 having end caps 11 and 12. A through shaft 15 is provided with a splined portion 19 which is engaged by a complementary portion of piston 23 which rides upon rods 26 which prevent the piston from rotating. In this reference the piston 23 performs the dual function of a power piston and drive nut. The power piston must be sealed not only against the inside diameter of the cylinder tube, but also at two locations where rods 26 pass through it. Additionally, the fluted inside diameter of the piston must be sealed against the flutes of the shaft. In applicant's device all fluid pressure sealing is isolated and confined to the power section thereby providing a complete separation of the power piston function from the drive nut thereby affording the opportunity to design these components with regard to their intended function without compromise.
The D. R. Ligh U.S. Pat. No. 3,499,342, dated Mar. 10, 1970, discloses a multiple motion converting actuator which, as illustrated in FIG. 4, comprises a shaft 3 having opposite ends journaled for rotary movement relative to the ends 11' and 14a' of a first cylinder 14'. A piston 25 is reciprocably mounted in a second cylinder 12. Torque heads 6 and 7 are secured, respectively to outer piston segments 26 and inner piston 25 by means of tie rods 29 and 32 which project through the innermost end wall of cylinder 14'. The outer surface of torque heads 6 and 7 are provided with splines which engage corresponding guides in the cylinder wall for precluding rotation of the torque heads incident to their movement between advanced and retracted positions. Each of torque heads 6 and 7 is provided with a through bore having teeth which engage the elongated splines 5 in the outer surface of the drive shaft. Fluid pressure media is adapted to be introduced into the outer end of a cylinder 12 for advancing the pistons 25 and 26 toward the drive shaft, and fluid media is adapted to be introduced via port 37 and the cylinder 14' for moving the pistons and their respective torque heads in the opposite direction relative to the drive shaft.
The R. O. Arvold U.S. Pat. No. 3,393,610, dated July 23, 1968, discloses a pressure-media operated torque actuator which comprises a power transfer part A and a converter section B which includes longitudinal splines 9, guides 10 and a nut-sleeve 11 which is secured to and carried by piston rod 14. An externally splined rod 3 passes through the inside diameter of piston 4, extends through piston rod 14 and threadably engages internal longitudal spline 9. Fluid media is introduced either through port 25 at the outer most end of portion A, or through port 24 at the outer most end of portion B, whereby the power and rotary functions are combined in what amounts to a single, elongate, two-step housing 7 & 8 which defines a single, pressurized vessel. The J. C. Miller U.S. Pat. No. 2,936,737, dated May 17, 1960 discloses a rotary actuator which comprises a single cylinder 10 having end caps 11. A rotable through shaft 18 is splined at 25 for engagement with complementary portions of piston 15, which is prevented from turning by means of elongate rods 13 which span the end caps and extend through openings in the piston.